Only variables referenced by a sub are captured by a sub. 

use strict;
use warnings;
use feature qw( say );

sub f { 
   my $x = shift;
   return sub { $x };
}

sub g { 
   my $y = shift;
   return sub { eval '$y' };
}

sub h { 
   my $z = shift;
   return sub { $z if 0; eval '$z' };
}

say f( 4 )->() // "[undef]";
say f( 5 )->() // "[undef]";
say "--";
say g( 6 )->() // "[undef]";
say g( 7 )->() // "[undef]";
say "--";
say h( 8 )->() // "[undef]";
say h( 9 )->() // "[undef]";

[download]
4
5
--
Variable "$y" is not available at (eval 1) line 1.
[undef]
Variable "$y" is not available at (eval 2) line 1.
[undef]
--
8
9

[download]

This is an optimization as capturing everything every time would have drawbacks.

I can't explain the behaviour you are seeing, but the bug you are encountering is surely related to this optimization.

In any case, adding the following to your outer eval works around the issue: 

my $v = $v;

[download]

In reply to Re: Lexical variable not available by ikegami
in thread Lexical variable not available by choroba

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.